Saturday, September 29, 2007

My 2006 paper is often criticized on one point. If Arctic environments did intensify sexual selection of women among ancestral modern humans, and if this selection did create inter alia the color traits of Europeans (diversification of eye and hair color, extreme depigmentation of skin color), then why are these traits absent among the native peoples of northern Asia and North America? Surely they too are products of Arctic environments.

Yes, they are. But it was not Arctic environments per se that intensified sexual selection of women. It was essentially two changes to the sexual division of labor that, among hunter-gatherers, generally correlate with distance from the equator. First, hunting distance increases with decreasing numbers of game animals per square kilometer, thereby increasing male mortality. Second, food gathering decreases with longer winters, thereby increasing women’s reliance on men for provisioning and increasing the costs of polygyny for men. It is this combination of higher male mortality and limited polygyny that intensifies sexual selection of women.

These points are made by Hoffecker (2002, pp. 7-8):

Hunter-gatherer diet is strongly influenced by latitude and temperature. To begin with, energy demands increase significantly in cold climates and caloric intake in arctic environments may be as much as 30 percent higher than it is in tropical regions. The percentage of meat and fish in the diet of recent hunter-gatherers increases as temperature, moisture, and primary productivity decline, and equals or exceeds 80 percent among most peoples who live in areas with an effective temperature of 10 degrees C or less. …

The high protein-fat diet and hunting and fishing subsistence of hunter-gatherers in northern environments has major implications for foraging strategy. Although cold maritime settings often provide rich concentrations of aquatic resources that require limited mobility, hunter-gatherers in northern continental environments who subsist on terrestrial mammals must forage across large areas in order to secure highly dispersed and mobile prey. Among peoples who rely primarily on nonaquatic foods, there is a correlation between temperature and the average distance of residential moves and a related correlation between the percentage of hunted food in the diet and territory size. Another consequence of low temperatures and a high meat diet is that males procure most or all food resources, generating a more pronounced sexual division of labor.

Hunting distance and male food provisioning of women seem to be at a maximum in a special kind of Arctic environment: ‘continental’ steppe-tundra, where almost all food is in the form of highly dispersed and mobile game animals. Today, this environment is confined to the northern fringes of continental Eurasia and North America. During the last ice age, it lay further south and covered more territory. This was especially so in Europe. The Scandinavian icecap had pushed the steppe-tundra zone far to the south and on to the broad plains stretching from southwestern France through northern Germany and into eastern Europe. This combination of treeless tundra and temperate latitudes created an environment quite unlike the northern barrens we know today. As Jochim (1983, p. 214) notes: “The low-latitude tundras and park-tundras of glacial Europe were richer than any modern northern counterparts.” Long intense sunlight favored a lush growth of mosses, lichens, and low shrubs that fed herds of large herbivores, mainly wild reindeer (a.k.a. caribou) but also mammoth, woolly rhinoceros, horse, bison, red deer, roe deer aurochs, ibex, chamois, saiga antelope, muskox, giant deer, wild ass, elk, and wild boar (Butzer, 1964, p. 138).

Though substantial, this kind of biomass is a volatile food source. Caribou herds in Alaska fluctuate considerably in any one area, in part because they cover long distances in the space of one year but also because they go through long-term demographic cycles of expansion and contraction (Burch, 1972). Among caribou-dependent Inuit, “at least 1 period of hunger or starvation is part of the normal annual cycle” (Burch, 1972, p. 350). In good times, caribou herds do provide a bountiful food source, but at the price of continual camp moves and extensive reconnoitering on foot. This is the real man-killer in Arctic groups that have not yet domesticated reindeer, as Krupnik (1985, p. 126) notes when explaining the Chukchi’s low ratio of men to women:

The herdsmen guarded the herd on foot. There were no herd dogs, and reindeer were not used for transport during the summer months, so that the men had to travel with the herds over the tundra with a minimum of portable possessions. All of this must have sharply intensified the physical burdens on adult, able-bodied men, and caused a higher mortality rate and consequently a proportional decrease of their numbers in the population.

Thus, on the steppe-tundra of the last ice age, the population of human hunters was probably as volatile as its resource base, all the more so if one also considers the climatic oscillations during this period. Moreover, because this population was dispersed over a wide area, its density was not necessarily high enough for long-term viability. Hoffecker (2002, pp. 8-10) writes:

The high mobility requirements of northern continental environments not only incur added time and energy costs, but also carry potential social and reproductive costs for dispersed populations in such environments. Populations must maintain a minimum threshold density in order to remain viable and avoid extinction, and it is estimated that the “minimum equilibrium size” for a mating network of modern hunter-gatherers is between 175 and 475 individuals. The degree of dispersal of these individuals across the landscape (typically grouped into bands containing roughly 25 individuals) cannot exceed their ability to sustain a social network through at least periodic contact and aggregation.

All of these factors hindered sustained human occupation. When temperatures fell during the last glacial maximum (19,000-18,000 BP), depopulation seems to have occurred throughout the steppe-tundra zone, but more so in some areas than in others. Least affected were the warmer and moister areas in Western Europe and the Carpathian basin, where continuous occupation is well attested throughout the glacial maximum (Hoffecker 2002, p. 194). Most affected were the colder and drier areas in northern Asia, where the steppe-tundra zone lay close to the Arctic Circle and far from the Atlantic. Goebel (1999) writes:

During the last glacial maximum (19 to 18 kya), Siberia was devoid of human populations, except perhaps in small refuges like the southern Yenisei or Transbaikal region. … The central Asian steppe also lacks archaeological sites spanning the last glacial maximum, suggesting that increased aridity, lower temperatures, and a lack of woody plants severely limited human settlement in this region as well.

Bioproductivity was clearly lower in northern Asia. This factor, on top of other factors affecting the entire steppe-tundra zone (volatile resource base, critically low density of human population), made any human presence vulnerable to extinction during periods of environmental stress. There likely were repeated cycles of colonization, extinction, and recolonization.

In conclusion, substantial and continuous human settlement seems to have been confined to the European end of the steppe-tundra zone. Only there did all conditions fall into place for sustained sexual selection of women.

Friday, September 21, 2007

While killing time in a bookstore, I came across Godless: The Church of Liberalismby Ann Coulter. According to the blurb: “Liberals' absolute devotion to Darwinism, Coulter shows, has nothing to do with evolution's scientific validity and everything to do with its refusal to admit the possibility of God as a guiding force.”

It’s news to me that liberals are devoted to Darwinism. I’ve seen just as much Darwin-bashing on the political left as I’ve seen on the political right. More so, in fact.

But another thing bothered me with Anne’s book. It was her equation of religion with conservatism, especially in the realm of social issues. She is not alone in this regard. Most social conservatives seem to feel that religion is their one and only mainstay. It’s almost as if they feel that their values must be accepted on faith alone and cannot be defended by rational argument.

… So in the American Conservative piece I wanted to offer some resistance to the assumption of conservative religious unanimity. I tried to point out that conservatism has no necessary relation to religious belief, and that rational thought, not revelation, is all that is required to arrive at the fundamental conservative principles of personal responsibility and the rule of law. I find it depressing that every organ of conservative opinion reflexively cheers on creationism and intelligent design, while delivering snide pot shots at the Enlightenment. Which of the astounding fruits of empiricism would these Enlightenment-bashers dispense with: the conquest of cholera and other infectious diseases, emergency room medicine, jet travel, or the internet, to name just a handful of the millions of human triumphs that we take for granted?

Is Heather Mac Donald less of a social conservative because she is not religious? Conversely, is the political right more socially conservative when it talks the talk of religious folk? Heather addressed these questions in her recent article “What is Left? What is Right?":

Skeptical conservatives--one of the Right's less celebrated subcultures--are conservatives because of their skepticism, not in spite of it. They ground their ideas in rational thinking and (nonreligious) moral argument. And the conservative movement is crippling itself by leaning too heavily on religion to the exclusion of these temperamentally compatible allies. Conservative atheists and agnostics support traditional American values. They believe in personal responsibility, self-reliance, and deferred gratification as the bedrock virtues of a prosperous society. They view marriage between a man and a woman as the surest way to raise stable, law-abiding children. They deplore the encroachments of the welfare state on matters best left to private effort.

They also find themselves mystified by the religiosity of the rhetoric that seems to define so much of conservatism today. Our Republican president says that he bases "a lot of [his] foreign policy decisions" on his belief in "the Almighty" and in the Almighty's "great gifts" to mankind. What is one to make of such a statement? According to believers, the Almighty's actions are only intermittently scrutable; using them as a guide for policy, then, would seem reckless.

Over thirty years ago, social conservatives hitched their wagon to religion through groups like the Moral Majority. They succeeded electorally, being key to the election of several right-of-center governments. Indeed, they—and not economic conservatives—have been the main voting base for such governments. Yet they have lost out to economic conservatives in shaping public policy. How come?

It’s just that most people out there don’t believe in the Bible. To win them over, you have to come up with something better than: “Because the Bible says so!” Faith-based arguments simply don’t cut it when the time comes to present talking points and influence policymaking.

Ann, it’s not because of Darwin that social conservatives today have so little impact. The fault lies more in the dubious alliances they’ve made in order to elect governments more responsive to their concerns. It also lies in not having arguments that make sense to secular people. Before lashing out at Darwin, you should take a cold hard look at this faith-based strategy. It isn’t working.

Friday, September 14, 2007

It is often assumed that Europeans have always looked much like they do now. Even Neanderthals are often depicted as white folk who need a shave and a haircut. Yet, clearly, Europeans have not always been European. At some point in time, their ancestors came from somewhere else and looked like people from somewhere else.

The current thinking is that modern humans arrived in Europe about 35,000 years ago by way of the Middle East and ultimately from Africa. When did these proto-Europeans begin to look like their present-day descendants? Probably long after. The current phenotype seems to reflect later in situ changes to morphology and coloration that are still far from uniform among Europeans.

In a study of prehistoric European skeletons, Holliday (1997) found that early Upper Paleolithic skeletons had ‘tropical’ body proportions and clustered with recent Africans. Late Upper Paleolithic and Mesolithic skeletons clustered with recent Europeans. The shift to a more European phenotype is placed by Holliday (1997) at around 20,000 BP— during the last ice age and well after the arrival of modern humans.

Even later are the changes to European skin color, eye color, and hair color. Whitening of the skin, through allelic changes at the AIM1 gene, is dated to about 11,000 years ago (Soejima et al., 2005). Allelic changes at other skin color loci are similarly dated to the late Upper Paleolithic or even the Holocene (Voight et al., 2006). No less recent is diversification of eye color alleles at the OCA2 gene (Voight et al., 2006). Diversification of hair color alleles at the MC1R gene has yet to be reliably dated but is likely contemporaneous. This whitening of the skin and diversification of eye and hair color clearly constitute an in situ evolution within Europe, being most prominent within a zone centered on the East Baltic and covering the north and the east. Within this zone, skin is unusually white, almost at the physiological limit of depigmentation, eyes are not only brown but also blue, gray, hazel or green, and hair is not only black but also brown, flaxen, golden or red. As one moves further east and south, these color traits disappear and merge into the standard human pattern of dark skin, brown eyes, and black hair.

If I had unlimited funding, I would like to retrieve nuclear DNA from European skeletal remains that date from the arrival of modern humans (c. 35,000 BP) to the near present (c. 5,000 BP). I would then study changes in genes for skin color, eye color, hair color, hair length and form, and facial morphology. My hunch is that all of these changes took place within a narrow time-frame, most likely between the glacial maximum (c. 20,000-15,000 BP, when Europe was largely depopulated) and the end of the last ice age (c. 10,000 BP).

These changes were driven not so much by adaptation to the natural environment as by intense female-female competition for mates. Men were in short supply among early Europeans, especially among those who pursued reindeer herds across the northern and eastern plains. This was because of 1) very long hunting distances, which greatly increased death rates among young men; and 2) limited opportunities for food gathering, which made women dependent on men for provisioning and thus ruled out polygyny for all but the ablest of hunters. With too many women competing for too few men, conditions were optimal for sexual selection of women. Men were able to translate their subtlest preferences into mate choice. Intense sexual selection is particularly indicated by a shift to brightly colored traits, especially color polymorphisms—such as those of eye and hair color (Frost, 2006).

How did Europeans look previously? They probably looked distinctly non-European. Holliday, as already discussed, noted the ‘tropical’ and even African appearance of early modern humans in Europe. Other anthropologists have noted the same, particularly in relation to a pair of skeletons discovered in 1901 at Grimaldi, northern Italy. The skeletons were initially dated to the beginnings of modern human occupation in Europe, c. 30,000 BP. Associated artifacts have since been radiocarbon dated to 14,000-19,000 BP but may come from more recent layers of occupation (Bisson et al., 1996).

These skeletons exhibit an array of dental and morphological characteristics normally found in sub-Saharan Africans. As Boule and Vallois (1957, pp. 285) report:

When we compare the dimensions of the bones of their limbs, we see that the leg was very long in proportion to the thigh, the forearm very long in proportion to the whole arm; and that the lower limb was exceedingly long relative to the upper limb. Now these proportions reproduce, but in greatly exaggerated degree, the characters presented by the modern Negro. …

The skulls likewise look non-European. The face is wide but not high. The nose is broad and flat. The upper jaw projects forward whereas the chin is weakly developed. The well-preserved dentition is not at all European. Among currently living populations, the ones who most closely resemble the Grimaldi humans seem to be the Khoisan peoples of southern Africa. Boule and Vallois (1957, pp. 290-291) write:

For our part, we have been greatly struck by the resemblances these Grimaldi Negroids bear to the group of South African tribes, the Bushmen and the Hottentots. Comparisons which we have been able to make with the material at our disposal, in particular with the skeleton of the Hottentot Venus, have led us to note, for instance, the same dolichocephalic character, the same prognathism, the same flattening of the nose, the same development of the breadth of the face, the same form of jaw, and the same great size of teeth. The only differences are to be found in the stature and perhaps in the height of the skull.

We know less about their soft-tissue characteristics. Alongside the skeletons were a number of female statuettes with big breasts, protruding bellies, full hips, and large buttocks. The hair seems to be short and matted (Boule & Vallois, 1957, p. 311).

These Grimaldi humans may have been ancestral to later European populations:

Verneau has investigated the survivals of the Grimaldi race at different prehistoric periods. He has first of all compared this type with the Cro-Magnon, which succeeded it in place. ‘At first sight’, he says, ‘the two races appear to differ greatly from each other; but on examining them in detail, we see that there is no reason why they should not have had some ties of kinship.’ Verneau even declares that the Grimaldi Negroids ‘may have been the ancestors of the hunters of the Reindeer Age’. (Boule & Vallois, 1957, p. 291).

Interestingly, Grimaldi-like humans are reported to have persisted in parts of Europe as late as the Neolithic:

Verneau likewise discovered, in both prehistoric and modern races, survivals or reappearances of the Grimaldi types.

‘In Brittany, as well as in Switzerland and in the north of Italy, there lived in the Polished Stone period, in the Bronze Age and during the early Iron Age, a certain number of individuals who differed in certain characters from their contemporaries’, in particular in the dolichocephalic character of their skull, in possessing a prognathism that was sometimes extreme, and a large grooved nose. This is a matter of partial atavism which in certain cases, as in the Neolithic Breton skull from Conguel, may attain to complete atavism. Two Neolithic individuals from Chamblandes in Switzerland are Negroid not only as regards their skulls but also in the proportions of their limbs. Several Ligurian and Lombard tombs of the Metal Ages have also yielded evidences of a Negroid element.

Since the publication of Verneau’s memoir, discoveries of other Negroid skeletons in Neolithic levels in Illyria and the Balkans have been announced. The prehistoric statues, dating from the Copper Age, from Sultan Selo in Bulgaria are also thought to portray Negroids. In 1928 René Bailly found in one of the caverns of Moniat, near Dinant in Belgium, a human skeleton of whose age it is difficult to be certain, but which seems definitely prehistoric. It is remarkable for its Negroid characters, which give it a resemblance to the skeletons from both Grimaldi and Asselar.

It is not only in prehistoric times that the Grimaldi race seems to have made its influence felt. Verneau has been able to see, now in modern skulls and now in living subjects, in the Italian areas of Piedmont, Lombardy, Emilia, Tuscany, and the Rhone Valley, numerous characters of the old fossil race (Boule & Vallois, pp. 291-292).

Although the concept of atavism or ‘throwback’ is no longer widely accepted, there may have been some human groups in Europe that still looked African long after most had moved away from this phenotype. Indeed, if sexual selection were the cause, the phenotypic transformation should have occurred unevenly, beginning among populations on the former steppe-tundra of northern and eastern Europe, and then percolating outward through gene flow. In some peripheral regions, the transformation may still have been incomplete at the dawn of history.

Observations similar to those of Boule and Vallois have appeared elsewhere in the literature. Angel (1972) noted that 14% of skeletal samples from early Neolithic Greece displayed apparently Negroid traits, in contrast to later periods.

To be sure, there is a lot of pooh-poohing in the literature about the Grimaldi skeletons. Some say that the skeletal restoration must have been defective, or that the pressure of overlying layers had distorted the skull and the jaw, or that the apparently Negroid traits are of the sort that occur sporadically in Europeans.

There was, in fact, only one Upper Paleolithic European race. It was Caucasoid and it inhabits Europe today. We know this not only from skeletons but also from the representations of the human body in Upper Paleolithic art.

These are dental characteristics of the Negro, but not exclusively. They are also seen on a number of teeth from Krapina and on those of Neanderthals, and are also present, as we have just mentioned, in the Mount Carmel population. An upper canine from the Magdalenian maxilla of Farincourt has the same features. The Grimaldi child was no more Negroid than the Palestinians of Skhul and many living Europeans of the Mediterranean region.

These statements are true, more or less. The dentition of sub-Saharan Africans does conserve many archaic characteristics that are absent in other modern humans but are present in Neanderthals, in the Skhul-Qafzeh hominins, and in other hominids (Irish, 1998). But the Grimaldi skeletons are clearly modern human. And while it is true that individual Negroid traits occur sporadically in living Europeans, it would be unusual, very unusual, for all of them to co-occur in a single living European. Finally, as Coon himself points out, other European skeletons from the Upper Paleolithic also show these traits.

Carleton Coon believed in the multiregional model of human evolution. He felt that European modern humans evolved out of European Neanderthals. So they could not have come from elsewhere. The Grimaldi skeletons, and others like them, must be an aberration … unless one accepts the ‘Out-of-Africa’ model. From the standpoint of this second model, we have one more piece in a puzzle linking modern Europeans to a demographic expansion that began to spread out of Africa some 50,000 years ago and that reached their continent about 35,000 years ago.

According to the Out-of-Africa model, the first modern humans in Europe could not have looked ‘white’. Indeed, they probably did not for at least the next 15,000 years. Their physical appearance seems to have changed, and radically so, within a later and relatively narrow time-frame, probably the second half of the last ice age.

The cause? It does not seem to have been natural selection, i.e., gradual adaptation to the ecological conditions of Europe. As I have discussed elsewhere, the cause is more consistent with an intensification of sexual selection of women, as a result of the unusually strong female-female competition for mates that prevailed among herd-hunting peoples in ice-age Europe. Since most genes are not sex-linked, this selection spilled over on to members of both sexes, thus modifying the appearance of the entire population (Frost, 2006).

Friday, September 7, 2007

I have almost finished writing a manuscript that will follow up on an earlier article published in 2006: "European hair and eye color - A case of frequency-dependent sexual selection?" Evolution and Human Behavior 27: 85-103. At this point, I should start planning my research sabbatical.

The research project itself is pretty much decided on. I wish to replicate a study I had published in 1994: "Preference for darker faces in photographs at different phases of the menstrual cycle: Preliminary assessment of evidence for a hormonal relationship", Perceptual and Motor Skills 79: 507-514. In this earlier study, I showed women several pairs of male facial photos, one of which had been made slightly darker than the other. Preference for the darker face was significantly higher among subjects in the estrogen-dominant phase of their menstrual cycle (i.e., the first two-thirds) than among those in the progesterone-dominant phase (i.e., the last third). This cyclic effect was absent in women on oral contraceptives and in women who were assessing pairs of female faces.

This study is poorly known, even among people who are interested in this sort of thing. It was pre-Internet (and is still unavailable online) and came out in a second-tier journal. Perhaps more importantly, I was working on my own with nobody to pitch my findings to a wider audience.

A team of psychologists at St. Andrews University (Scotland) replicated most of my findings in 2005 before learning about my earlier study (Jones, B.C., Perrett, D.I., Little, A.C., et al. 2005. "Menstrual cycle, pregnancy and oral contraceptive use alter attraction to apparent health in faces", Proc. R. Soc. B 272:347-354). As part of a broader research effort—the effects of “apparent health” on mate choice—they presented women with pairs of male faces that slightly differed in shape, color, and texture. Their subjects’ preferences showed the same variation with menstrual cycle that I had observed. Unfortunately, they did not try to identify which physical difference was driving this cyclic change in preference. It was probably the difference in skin color, but it might also have been the difference in skin texture or facial shape.

I hope to replicate my earlier study, but this time with a much larger pool of subjects and better photos (color and not B/W). I also hope to determine which skin pigment is driving this cyclic change. Is it male ruddiness (i.e., hemoglobin) or male brownness (i.e., melanin)? And just what component of ‘preference’ is being affected? Just what are the psychological effects of minor variation in skin color within the context of male-female interaction?

The obvious research location would be St. Andrews University. In fact, I had earlier applied to do research there and been accepted. But that was three years ago. A number of personal problems have since intervened, notably the settlement of my late mother’s estate. Now, with these problems out of the way, I have to reassess things.

Going to St. Andrews offers several advantages:

1. The investigators there are already familiar with this line of research.

2. Their research center has state-of-the-art equipment and is staffed with some of the best minds in cognitive psychology.

3. Language would not be a problem. I could easily find my way around after a short period of adaptation. The British are helpful people and make good research associates.

But there are disadvantages:

1. Academics at St. Andrews are busy people who are already overwhelmed with their own research work. I remember a piece of advice I was given during my doctoral studies: “It’s better to choose a supervisor who is less prestigious but who will spend time with you and be willing to go to bat for you, especially for things like grant proposals and job openings.”

2. The investigators there are working within a paradigm that differs somewhat from my own. They see skin color as an index of health (pale skin = bad health, dark skin = good health, cf. Hamilton and Zuk hypothesis). My feeling is that other mental algorithms are involved. This is something of a fault-line between “adaptationist” and “non-adaptationist” views of mate choice and sexual selection. If I’m not careful, I could be stigmatized as a “non-adaptationist.”

3. The offer from St. Andrews did not come with a scholarship. I would have to pay my own expenses in a country that has one of the highest costs of living in the world.

4. The word “skin color” automatically calls to mind issues of race and ethnicity. This is especially so in Great Britain. I could easily be caricatured as a “race scientist” or some such animal.

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Welcome to my blog! For the most part, this page will be an extension of my website, with comments relating to my research. But it will also branch out into more general discussions of human evolution.